Globally, female sex workers (FSW) are at disproportionate risk for violence, HIV, and substance use. Though many studies have shown that violence imparts HIV risk, little is known about how different forms of violence interact in te lives of sex workers to produce sexual and drug-related HIV risk. The proposed mentored research will examine the association of four dominant forms of abuse (intimate partner violence, client violence, pimp violence, and police violence) with the predominant modes of HIV transmission in this population (unprotected sex and injection drug use), identifying forms of violence that synergistically increase the risk of HIV when they occur together (syndemic effect). The study will use data from sex workers (n=754) in Russia, one of few countries where HIV prevalence and AIDS deaths are still increasing. The study will first assess the prevalence of experiencing multiple forms of violence (polyvictimization) and the relationship between different types of violence. This will show how multiple forms of violence cluster and what demographic groups are most at risk for specific violence clusters. Then, after exploring the individual association of each type of violence with the outcomes, two analytic approaches will be used to explore how sexual and drug-related HIV risk increases as the number of types of violence FSW are exposed to accumulates. First, dose-response techniques will quantify the relationship between the number of types of violence experienced and sexual and drug-related HIV risk. Additionally, multivariate regression analysis will be used to quantify the impact of each form of violence on unprotected sex and injection drug use, using interaction terms to identify synergistic effects between different forms of violence. This study provides a basis for understanding the nature and extent of polyvictimization in propagating HIV and substance use risk in the context of sex work. This research incorporates elements of syndemic and polyvictimization frameworks, both of which have been underutilized in sex work contexts, and extends quantitative methods typically used with these frameworks via the use of interaction terms. Despite WHO calls for violence interventions as a critical component of HIV prevention, violence has not been consistently or comprehensively integrated into HIV and substance abuse research. This study will inform assessment of and intervention on distinct forms of violence in future research and in service provision for HIV and substance abuse among FSW. The proposed dissertation research and training plan leverage the rigorous classroom training and faculty mentorship at Johns Hopkins and will advance the trainee's career goals of becoming an independent investigator and developing evidence-based approaches to reduce substance abuse, violence, and HIV in marginalized populations.